The seal is a useful tool for the identification of a person in the Chinese and the Japanese society. A seal always contains a frame and several characters. The characters represent the name of a person or other expressions. Sometimes the characters are printed positively and sometimes are printed reversed. A seal print is attached to a document after the document is prepared to make it a formal one. In many cases, the seal print is deemed equal to or more important than the signature of a person. When a seal is printed to a document, the color of the seal print is always red or pink. Most documents are not written or printed in red color. Therefore, the seal print or prints on a document are obvious to readers of the document.
An automatic matching device for seal prints is desirable in locations where a large quantity of seal prints shall be identified. Take the bank as an example. When a customer of a bank opens a savings account in the bank, the customer is required to register a sample seal print at the bank. When the customer withdraws money from the account, he will be required to print the same seal on the notice of withdrawal. A teller of the bank will then compare the seal print with the sample seal print and decide whether the two seal prints are identical (or are from the same seal). When they are decided to be identical or matched, the customer will be allowed to withdraw the money.
Two kinds of automatic matching devices for seal prints have been developed and provided to help the bank tellers to match seal prints:
Semi-automatic matching device: The sample seal prints are stored in the matching device. When a seal print is to be matched, its corresponding sample seal print is retrieved and its image is displayed on a monitor. An image capture device is used to capture the image of the seal print to be matched. The captured image is also displayed on the monitor, in a different color. The teller adjusts the position of the seal print to be matched such that two images overlap. Differences between the two images are identified and the teller decides whether they are identical according to the characteristics of the differences.
Automatic matching device: When seal prints are being matched automatically, it is never necessary to compare the whole images. The sample seal prints are stored in the matching device with their feature points. When a seal print is to be matched, its image is captured by an image capture device and its feature points are abstracted. The feature points of the seal print to be matched are then compared with that of its corresponding sample seal print. An algorithm is used to decide the similarity of the two seal prints. When the similarity value is greater than a threshold, the two seal prints are considered identical or matched.
Taiwan patent application No. 85108751 which corresponds to U.S. Pat. No. 5,960,112 disclosed an "automatic seal print matching system". This invention determines automatically whether two seal prints are from the same seal according to "similarity in image structure", "similarity in line distribution", "index of similarity" and "incompleteness". Although this invention provides accurate matching of seal prints, it requires to complicated calculations and uses large memory space. As a result, its drawbacks include long processing time and high manufacture cost.
It is thus necessary to provide a simplified method and device for automatic matching of seal prints to enhance the matching speed.
It is also necessary to provide a novel method and device for automatic matching of seal prints that uses relatively smaller memory space.
It is also necessary to provide a simplified method and device for automatic matching of seal prints that provide accurate matching results.